Optical instrument for imaging and sensing using multicore fiber

ABSTRACT

Disclosed herein are configurations for fiber optic endoscopes employing fixed distal optics and multicore optical fiber.

RELATED APPLICATION SECTION Related Application Section

The present application is a continuation of U.S. patent applicationSer. No. 16/704,851, entitled “Fixed Distal Optics Endoscope EmployingMulticore Fiber”, filed on Dec. 5, 2019, which is a divisionalapplication of U.S. patent application Ser. No. 15/147,775, entitled“Fixed Distal Optics Endoscope Employing Multicore Fiber”, filed on May5, 2016, which claims priority to U.S. Provisional Application Nos.62/166,154 filed on May 26, 2015, 62/163,522 filed on May 19, 2015,62/163,532 filed on May 19, 2015, and 62/157,131 filed on May 5, 2015.The entire contents of U.S. patent application Ser. Nos. 15/147,775, and16/704,851 and U.S. Provisional Application Nos. 62/166,154, 62/163,522,62/163,532, and 62/157,131 are herein incorporated by reference.

TECHNICAL FIELD

This disclosure relates generally to endoscopic devices and inparticular to a fixed distal optics endoscope having multicore fiber.

BACKGROUND

Medical and non-medical applications of imaging endoscopes are wellknown and their importance to contemporary cardiology, gastroenterology,pulmonology, laparoscopy as well as nondestructiveevaluation/nondestructive testing (NDE/NDT) is widely accepted. Giventhat importance, improvements to endoscopic devices and systems wouldrepresent a welcome addition to the art.

SUMMARY

An advance in the art is made according to an aspect of the presentdisclosure directed to endoscopic devices employing multicore opticalfiber.

In contrast to contemporary, prior-art endoscopic devices and systems,devices constructed according to the present disclosure may employ—inaddition to multicore optical fiber—employ a variety of measurementtechniques including swept-source techniques, employ widely tunablesource(s), include multiple functions, and—in some embodiments—criticalcomplex optical functions may be performed by one or more photonicintegrated circuit(s).

An illustrative endoscopic system and structure according to the presentdisclosure includes an optical receiver selected from the groupconsisting of spectral domain optical coherence tomography (OCT)receiver, time domain OCT receiver, confocal receiver, fluorescencereceiver, and Raman receiver; an endoscope body including fixed distaloptics; and a multicore optical fiber optically coupling the fixeddistal optics to the receiver.

Notably, term endoscope is used throughout the disclosure to describestructures according to the present disclosure. Those skilled in the artwill readily appreciate that the disclosure is not specifically limitedto endoscopes. More particularly, the disclosure and underlyingprinciples herein are equally applicable to catheters, laparoscopes,imaging guidewires as well as other medical and non-medical devices andstructures. Accordingly, when the term endoscope is used, it is intendedthat it be interchangeable with any instrument or system used to examinethe inside of something—oftentimes a body for medical reasons. Suchinstruments advantageously permit the interior of an organ or othercavity of the body. Of further advantage, endoscopes are capable ofbeing inserted directly into an organ for subsequent examination.

BRIEF DESCRIPTION OF THE DRAWING

A more complete understanding of the present disclosure may be realizedby reference to the accompanying drawings in which:

FIG. 1 shows exemplary Prior Art endoscopes;

FIG. 2(A), FIG. 2(B) and FIG. 2(C) show a series of exemplarysingle-mode fiber scanning endoscopes as known in the Prior Art;

FIG. 3 shows a schematic diagram of a multi-core fiber endoscopeemploying an array of swept-source optical coherence tomography (SS-OCT)receivers according to an aspect of the present disclosure;

FIG. 4 shows a schematic diagram of a multi-core fiber endoscopeemploying a single SS-OCT receiver and distinct delays according to anaspect of the present disclosure;

FIG. 5 shows a schematic diagram of another multi-core fiber endoscopeemploying a single SS-OCT receiver and 1:N switch(es) interconnectingthe receiver to the endoscope according to an aspect of the presentdisclosure;

FIG. 6 shows a schematic diagram of an illustrative distal portion of afive-core optical fiber endoscope according to an aspect of the presentdisclosure;

FIG. 7(A), FIG. 7(B), FIG. 7(C), FIG. 7(D) and FIG. 7(E) show a seriesof illustrative arrangements as schematic diagrams other illustrativemulti-core fiber endoscope employing: FIG. 7(A) a collimating lens, FIG.7(B) a fiber/lens coupling element including a passive or active beamsteering elements, FIG. 7(C) a graduated index (GRIN) lens or section ofmultimode fiber, FIG. 7(D) a multi-element collimating lens, and FIG.7(E) a beam deflector element according to aspects of the presentdisclosure;

FIG. 8 shows a schematic diagram of an illustrative multi-core fiberendoscope wherein the multi-core fiber is connected to a photonicintegrated circuit (PIC) according to an aspect of the presentdisclosure;

FIG. 9 show another schematic diagram illustrating a multi-core fiberendoscope wherein the multi-core fiber is connected to a PIC accordingto an aspect of the present disclosure;

FIG. 10 shows yet another schematic diagram illustrating a multi-corefiber endoscope wherein the multi-core fiber is connected to a PICaccording to an aspect of the present disclosure;

FIG. 11 show a schematic diagram illustrating a multi-core fiberendoscope having a pull-back and/or rotational or twisting proximalmotor according to an aspect of the present disclosure;

DETAILED DESCRIPTION

The following merely illustrates the principles of the disclosure. Itwill thus be appreciated that those skilled in the art will be able todevise various arrangements which, although not explicitly described orshown herein, embody the principles of the disclosure and are includedwithin its spirit and scope. More particularly, while numerous specificdetails are set forth, it is understood that embodiments of thedisclosure may be practiced without these specific details and in otherinstances, well-known circuits, structures and techniques have not beenshown in order not to obscure the understanding of this disclosure.

Furthermore, all examples and conditional language recited herein areprincipally intended expressly to be only for pedagogical purposes toaid the reader in understanding the principles of the disclosure and theconcepts contributed by the inventor(s) to furthering the art, and areto be construed as being without limitation to such specifically recitedexamples and conditions.

Moreover, all statements herein reciting principles, aspects, andembodiments of the disclosure, as well as specific examples thereof, areintended to encompass both structural and functional equivalentsthereof. Additionally, it is intended that such equivalents include bothcurrently-known equivalents as well as equivalents developed in thefuture, i.e., any elements developed that perform the same function,regardless of structure.

Thus, for example, it will be appreciated by those skilled in the artthat the diagrams herein represent conceptual views of illustrativestructures embodying the principles of the invention.

In the claims hereof any element expressed as a means for performing aspecified function is intended to encompass any way of performing thatfunction including, for example, a) a combination of circuit elementswhich performs that function or b) software in any form, including,therefore, firmware, microcode or the like, combined with appropriatecircuitry for executing that software to perform the function. Theinvention as defined by such claims resides in the fact that thefunctionalities provided by the various recited means are combined andbrought together in the manner which the claims call for. Applicant thusregards any means which can provide those functionalities as equivalentas those shown herein. Finally, and unless otherwise explicitlyspecified herein, the drawings are not drawn to scale.

Thus, for example, it will be appreciated by those skilled in the artthat the diagrams herein represent conceptual views of illustrativestructures embodying the principles of the disclosure.

By way of some additional background, it is noted that many contemporaryimaging endoscopes, catheters, laparoscopes, and imaging guidewires—suchas those employed in optical coherence tomography systems—typicallyemploy single mode optical fiber. Such systems perform scanning andimaging by either: 1) spinning the fiber or 2) employing distaloptics—for example, motor(s) and actuator(s)—along with a stationarysingle mode optical fiber. As may be appreciated, configurations suchas 1) and 2), above, provide necessary beam deflection(s) to effect thescanning.

Turning now to FIG. 1 there is shown several illustrations ofcontemporary optical endoscopes that are known in the art. While notspecifically identified in that Figure, such endoscopes may include aneyepiece, a light post, and an objective assembly. Alternativeconfigurations may include—among other things—an access port forinstrument(s) and an “umbilical” connection.

FIG. 2(A), FIG. 2(B) and FIG. 2(C) show in schematic form severalillustrative examples of single-mode, or multi-mode fiber scanningendoscopes as known in the art. As may be appreciated such endoscopesmust be capable of delivering, focusing, scanning and collecting asingle spatial-mode optical beam. In addition, the catheter employedoftentimes is flexible—but not always—and has a sufficiently smalldiameter to facilitate its entry into internal spaces such as arteries.Generally, such endoscopes will include optical control and couplingelement(s) at a proximal end, a single-mode fiber running the length ofthe catheter, and optical focusing and beam directing elements at thedistal end. As is generally known by those skilled in the art, theendoscope is configured to scan the beam in a circumferential patternsuch that a cross-section image may be made of structure(s) into whichit is positioned such as—for example—an artery.

As shown in FIG. 2(A), such illustrative examples generally include—at aproximal end—a system 210 which may include light source(s), detector(s)and controlling circuitry and/or operating software(s). Such a system isoptically, mechanically, and electrically coupled to a catheter body 230by a rotary fiber optical joint 220 which includes a spinning opticalfiber 231 which in turn is connected—at a distal end—to one or morelens(es) 240 and prism 241 which in turn produces a spatial mode opticalbeam 250.

The illustrative example shown in FIG. 2(B) includes—at its proximalend—system 212, stationary fiber optical joint 213 which is coupled tocatheter body 232 and includes a fixed, or stationary, otherwise nonspinning single mode optical fiber 233 which in turn is coupled—at thedistal end—to one or more lens(es) 242 which in turn is opticallycoupled to a prism 243 which is spun by distal motor 253.

Similarly, the illustrative example shown in FIG. 2(C) includes system214, stationary fiber optical joint 224, catheter body 234 includingstationary single mode optical fiber 235 optically coupled at a distalend to lens(es) 244 and optical phased array(s) 245 thereby producingscanning beam 256.

As may be appreciated, spinning optical fibers—such as those employed inconfigurations such as that in FIG. 2(A), exhibit several disadvantagesincluding non-uniform rotation distortion (NURD), fragility/breakage,cost, reliability, rotational speed limitations along with certainsafety considerations that accompany such configurations. Distalmotors—such as those employed in FIG. 2(B)—likewise are disadvantaged bycost, size, scanning flexibility, the need for control line(s) and powerdelivered to the distal end. Distal optical phased arrays—such as thoseemployed in FIG. 2(C)—while offering optimistic promise neverthelessexhibit limitations with respect to image quality, efficiency sidelobes,electrical power requirements and size.

Given such noted infirmities with these prior art endoscopes, scanningoptical endoscopes exhibiting low cost, small size and acceptable(albeit lower) scanning resolution may be may be constructed accordingto aspects of the present disclosure. More particularly, and withreference to FIG. 3 , there is shown in schematic an illustrativemulti-core fiber endoscope 300 according to an aspect of the presentdisclosure employing an array of swept-source optical coherencetomography (OCT) receivers. As shown in that figure, a multi-coreoptical fiber is employed and—in sharp contrast to the prior art—nodistal mechanical element(s), controllable phased array(s), and/orspinning fibers are used. Of further advantage, individual opticalfibers employed may be single-mode fiber(s) or multi-mode fiber(s). Itis noted at this point that while specific illustrative examplesdisclosed herein employ SS-OCT systems and techniques—the disclosure isnot so limited. More particularly, other OCT systems and non-OCT systemssuch as Raman, fluorescence, near-infrared, confocal, and other types ofimaging systems that connect similar multicore fiber endoscopes withmulticore optical fiber are contemplated and within the scope of thisdisclosure as well.

A multi-core fiber (MCF) has multiple cores positioned within acladding. Such MCF have been employed in telecommunications applicationsand shown considerable promise. Advantageously, the number of corescomprising a MCF may differ from application to application—as thoseindividual application needs dictate. By way of illustrative exampleonly—a seven core MCF may have one center and six outer cores. Thedistance between two neighboring cores is known as the core pitch. Byaltering the core pitch—it is known by those skilled in the art—that theamount of crosstalk between neighboring cores may be changed.

In the illustrative example shown in FIG. 3 , a swept-source opticalcoherence tomography system 310 is coupled to a multi-core optical fiberendoscope 330. As previously noted either single-mode or multi-modefibers may be employed however for SS-OCT systems such as the oneillustrated single-mode fibers are preferably used. Additionally, and aspreviously noted, while we have shown illustratively an SS-OCT system inthis Figure and described in this description, those skilled in the artwill readily appreciate that any of a variety of measurement system(s)may be employed and remain consistent with one or more aspect(s) of thepresent disclosure.

As depicted in FIG. 3 , a swept source laser 312 is split into Ndifferent channels through the effect of splitter 313 or other suitableoptical structure(s), each of the N channels optically coupled to amulti-core optical fiber 324 via a proximal end connected (shown inFigure as a dotted line). The N channels are conveyed via the multi-coreoptical fiber to distal optical structure(s) 370 that may focus lightthrough a transparent, protective cover 360—or transparent windows in atransparent cover—such that output light 380 is conveyed into anyexternal sample, i.e., body tissue(s) or cavities.

As will be now understood, light reflected from the sample(s) iscollected along the same optical path(s), combined with light directedto a reference arm 315 and interferometrically detected in N separate,opto-electronic receivers 316(1) . . . 316(n), the output of which isdirected into a digital signal processing sub-system 317 and othercomputer(s), controller(s), instrumentation—as necessary (notspecifically shown)—for analysis and/or display. Notably, an endoscopesuch as the one illustrated 330 may include a protective and/orstructural jacket 340 to ensure integrity and/or smoothoperation/insertion of the device as it is routed through otherinstruments or directly into a body lumen or other sample environment.Of further note that while this portion of the description has beendirected to an SS-OCT type system those skilled in the art willappreciate that systems according to the present disclosure are not solimited. In particular, other types of optical sensing, ranging, orimaging modalities may be employed (e.g., fluorescence, Raman,near-infrared spectroscopy, etc.) in systems according to the presentdisclosure.

As may be further appreciated by those skilled in the art, the distaloptical structures may advantageously include one or more passive lensassemblies or photonic integrated circuit(s) (PIC). Additionally, planarlightwave circuits (PLC) comprising those optical structures mayadvantageously be fabricated from InP or Si photonic materials—amongothers. By employing one or more PICs fabricated from well-knownmaterials using highly evolved fabrication technologies contemporarydesign tools may be employed to design, simulate and manufacture thedistal optical structures while producing benefits related to highprecision, small size and low-cost. Still further, such distal opticsaccording to the present disclosure may be fabricated—either in whole orin part—from molded optical materials and components thereby furtherlowering their cost and manufacturability.

Notably, while the distal optics of the system so described may compriseone or more PICs—so may elements of the SS-OCT portion 310 of thesystem. More particularly, on one illustrative embodiment according tothe present disclosure—the SS-OCT portion of the system 310 shownschematically within the dotted line of FIG. 3 , (excluding anyelements/components not suitable for PIC fabrication presently—i.e.,computers, etc.) may comprise one or more PICs such that a compact,robust, low-cost structure(s) result. As those skilled in the art willfurther appreciate and as will become apparent to those skilled in theart, such PIC fabrication methodologies may advantageously be applied toother designs/configurations according to the present disclosureincluding those described herein.

Of particular interest to those skilled in the art is that whileemploying a PIC a vertical cavity surface emitting laser (VCSEL) orother laser structure such as verner tuned laser may be integrated intoan SS-OCT PIC such that a single PIC includes a VCSEL transmitter,waveguide(s) for beam handling and one or more optical receivers such asa dual-balanced, dual-polarization, I/Q receiver—among other(s). Insharp contrast to contemporary configurations, such PICs may be designedso that VCSEL emission light is coupled into a silicon waveguide.

With reference now to FIG. 4 , there is shown a schematic of anillustrative embodiment of a multi-core fiber endoscope system 400employing a single SS-OCT receiver and distinct delay(s) according to anaspect of the present disclosure. As depicted in that Figure, a singlereceiver 410 is employed and SS-OCT information from each optical fibercomprising the multi-core fiber 425 is extracted through the utilizationof distinct delays 414 (D Dn). By employing different delays in eachfiber path, information about optical properties from each path istransformed into distinct intermediate frequencies (i.f.) at anyphotodetector(s) used. Such an approach of encoding two signals intodifferent i.f. frequencies has been employed in polarization sensitiveOCT (PS-OCT) but has not—prior to the present disclosure—been employedin optical endoscopes and in particular not in conjunction withmulti-core optical endoscopes according to the present disclosure.

As may be appreciated with continued reference to FIG. 4 , DSP unit 417may process these n distinct i.f. frequencies as they arrive asdifferent—and substantially non-overlapping—frequency bands. Thoseskilled in the art will readily appreciate that such a configurationresults in considerable advantage over the prior art as it utilizes onlyone receiver and exhibits only a 1/n loss in reflected signal power andtransmitted power. Note further that while this illustrativeconfiguration is shown, those skilled in the art will now appreciatefrom this disclosure that alternative configurations according to thepresent disclosure may be constructed that achieve the same result(s).

Similar to the system shown previously with respect to FIG. 3 , thereceiver 410 is coupled to the endoscope 430 by the multicore opticalfiber 425, wherein each of the individual fibers comprising themulticore optical fiber includes one or more distinct delay elements 414(D . . . . Dn) which produces a distinct delay for each of theindividual fibers. The endoscope 430 generally includes a body—providinga protective and structural jacket 440 to the multicore fiber 425 aswell as other elements positioned therein and comprising the overallendoscope 430. Notably, distal optics 470 produce optical scan beams 480and is generally protected through the effect of cap, 460. As willbecome apparent to those skilled in the art, a variety of distal opticalconfigurations are contemplated according to the present disclosure.

FIG. 5 shows yet another illustrative embodiment of a multi-core opticalendoscope system 500 according to the present disclosure wherein anillustrative SS-OCT sub-system 510 is coupled to a multi-core opticalfiber endoscope sub-system 530 through the effect of a 1:N switch 524.As depicted in that Figure, the illustrative sub-system 510 includes anumber of circulators 514 along with receiver 516 and DSP 518 forreceiving and processing return signals from samples illuminated bybeams 580 and under examination by endoscope system 500. In a particularillustrative embodiment of the system 500 shown in the Figure,repetition rate of laser 512 may be synchronized to the switching rateof the 1:N switch 524 such that light is transmitted and receivedsubstantially during a single frequency sweep (or multiple thereof). Inthis manner, inefficiencies associated with switching dynamics areincurred during a period when the laser is blanked—at lower power. Inthis manner, unused portion(s) of the laser frequency sweep isoverlapped in time with unusable portions of the switching duringswitching transients.

With this disclosure, those skilled in the art will readily appreciatethat this approach has the advantage of higher optical sensitivity asall of the laser light and sample reflected light is coupled to one (ormore) of the optical fibers comprising the multi-core optical fiber. Asnoted previously, other alternative optical systems and components suchas spectral-domain OCT, time-domain OCT, confocal systems, fluorescencesensors, Raman sensors and other may be used in place of the SS-OCTsystem shown illustratively. Of course, the SS-OCT system including the1:N switch may be constructed using integrated optical technologies—e.g.silicon photonics—to achieve a compact, reliable, low-cost system.Similarly—and as noted previously—these sametechniques/structures/methodologies may be employed with any/all of theillustrative examples disclosed herein.

Turning now to FIG. 6 , there is shown in schematic form anotherillustrative embodiment (both side and end view(s)) of a distal end ofmulti-core fiber endoscope 600 according to an aspect of the presentdisclosure. As may be observed from that Figure, the distal end of theendoscope includes a protective cap 670 and distal optics includingcollimating lens(es) 673, fold mirrors 672, and substrate 671 coupled tothe multi-core fiber, 625 which in this illustrative embodiment includes5 (five) single optical fibers shown arranged as a central fiber withfour perimeter fibers. Of course, those skilled in the art willappreciate that the number of individual fibers and number(s) ofindividual distal optical elements may be changed as specificapplication needs dictate. Additionally, the arrangement of theindividual fiber(s) and distal optical element(s) may change fromapplication to application as well. Shown further in that Figure is thelight beam patters 675 which emanate from the distal optics.

With continued reference to FIG. 6 —and as will be appreciated by thoseskilled in the art—certain details of structural and protective jacket(body) of the endoscope is not shown for simplicity. Operationally,light emanating from each fiber core is collected and directed intotissue/structures through the effect(s) of lens(es) 673 and mirrors 672.Notably, while the term “mirrors” is used herein—the disclosure is notso specifically limited. Other optical structures which redirect and/orthe light in a desired manner such as prisms, light guides, photonicintegrated circuits, etc., are contemplated for such structures andpurpose as well.

Accordingly, there exist numerous approaches to the distal optics of amulti-core fiber optic endoscope according to the present disclosure. Inparticular, lens(es) may be graduated index (GRIN) lenses, ball lenses,fiber lenses, and/or lens arrays including multimode, multicore fiberlens that may be affixed or fusion spliced to the distal end of themulti-core fiber. Optional fold mirrors (or prisms or other structures)may be used to redirect light from optical fiber core(s) substantiallyaway from endoscope axis—as desired. Also, one or more center cores maybe coupled to optical structures (lenses, etc) that direct lightsubstantially along the endoscope axis.

Advantageously, and as will be readily appreciated by those skilled inthe art, all distal optical elements—or selected components thereof—maybe made from discrete components, one or more molded components,photonic integrated circuit(s) or combinations thereof. As shown in theFigure(s), a protective cap may be fully or partially transparent orinclude windows to allow light to traverse from optical fibers and/oroptical elements to/from samples under examination while providing asmooth, sufficiently strong, and appropriately shaped character suchthat it may be presented/inserted/retrieved from anticipated pathwayssuch as the interior of a bodily lumen. Furthermore—as shown in FIG. 6 ,the entire distal optics may be assembled and/or fabricated as part ofor on top of a substrate. Advantageously, the substrate may allow beamexpansion from fiber to lens(es) such that a desired focus, beam waistetc. may be realized. As an illustrative example—and not consideredlimiting—if a multicore fiber is operating in a single mode regime at1300 nm, then the core size is ˜9 um. As is known in the art, to aachieve a ˜20 um beam waist (1/e{circumflex over ( )}2) at a ˜1 mm focallength requires ˜28 um diameter (1/e{circumflex over ( )}2) at a face ofa lens (in air). Longer focal lengths require a correspondingly largerbeam diameter at the lens face where requires a larger lateralseparation between fiber cores in the multicore fiber. As may beappreciated, it is desirable that light propagating along the fibercores and up to and out of any lense(s) does not have substantialleakage from one channel to another.

Of further note, alternative illustrative embodiments of the arrangementof FIG. 6 may not necessarily include the lens(es) depicted in thatFigure. In particular, one or more fold mirrors may be employed toredirect light into/away from the fiber axes—as appropriate.Advantageously, such a configuration is not only simple, but limitedimaging range may be achieved (˜0.3 um the Rayleigh range assuming a1310 nm wavelength and a ˜9 um beam waist at fiber facet).Accordingly—and as will be readily understood by those skilled in theart—there are a variety of other focal length/focal spot size width exitbeam diameter design tradeoffs that may be made depending on the desiredoperating parameters.

As may be appreciated, there are many medical and non-medicalapplications that would benefit from a simple, low-cost, compact,reusable and/or disposable endoscope such as one(s) constructedaccording to the present disclosure. Such applications include where aprecise, continuous profile of an intimal surface of a lumen is notneeded but a measurement of 2, 4, or 8 cross sectional dimensions of thelumen opening is sufficient. For example, when using a nine core opticalfiber with one fiber as a central fiber and eight fibers positionedconcentrically around the perimeter of that central fiber—each perimeterfiber having a fold mirror associated with it—then four cross-sectionalmeasurements along the 0, 45, 90 and 135 degree axis may be made alongwith one forward axial measurement. Such measurement(s) may be combinedwith fiber pull-back mechanism(s) to pull (or push) the endoscopesubstantially along the axis of the fiber. As will be shown anddiscussed, it is possible to perform a manual or automated twistingaction—back and forth—to sample more of the circumferential area ofinterest. In this manner four cross-sectional measurements maycontinuously be made as the endoscope/fiber is pulled back. Suchmeasurement(s) may be useful for a variety of applications includingsizing lumens for stents or other therapeutic or interventionalprocedures. Of further advantage, such endoscope(s) may be combined withother measurement devices/techniques including optical measurements(fluorescence, NIR, Raman) or non-optical devices (e.g., pressure,temperature, pH, etc.) It is also possible to combine such device(s)with therapeutic devices such as surgical lasers, cryo or RF ablation,mechanical cutting tools, and/or other devices/structures. Of distinctadvantage, it is possible to position such devices within the inside ofa needle—due to its small size.

FIG. 7(A), FIG. 7(B), FIG. 7(C), FIG. 7(D) and FIG. 7(E) show a seriesof illustrative arrangements as schematic diagrams other illustrativemulti-core fiber endoscope employing: FIG. 7(A) a collimating lens, FIG.7(B) a fiber/lens coupling element including a passive or active beamsteering elements, FIG. 7(C) a graduated index (GRIN) lens or section ofmultimode fiber, FIG. 7(D) a multi-element collimating lens, and FIG.7(E) a beam deflector element—as part of distal optics all according tocertain aspects of the present disclosure.

More particularly FIG. 7(A) shows another illustrative example of amulti-core fiber endoscope 700 according to the present disclosurewherein a single, shared collimating lens 710 is employed to collimatemultiple outputs 715 from multi-core optical fiber 730. Advantageously,the lens may be a single element lens that is coupled to the multi-corefiber 730 via a free-space or solid coupling mechanism(s) 720 includingdirect fusion splice of a graded index lens constructed of optical fiberor cementing a GRIN lens to the end of the multi-core fiber. Of furtheradvantage, the lens so coupled may be a single element or multiple,separate elements. Such lens(es) may be a GRIN lens, ball lens oraspheric molded glass lens—among other types as well. One additionalpossibility is the construction of lensing element(s) using fibergratings within the core or cladding material of the multi-core fiber.

With reference now to FIG. 7(B), there is shown yet another illustrativeexample of a multi-core fiber endoscope 701 according to an aspect ofthe present disclosure wherein a fiber/lens coupling element 720includes a passive or active beam steering element(s) 721, i.e., a prismelement, to adjust the focus location of light emanating from each ofthe individual fibers comprising the multi-core fiber (shown emanatingonto a collimating lens 710) such that the focus location(s) are nearlyidentical with respect to any sample(s) being examined.

Advantageously, there are a number of approaches to this illustrativeexample. In particular, if there are N cores in the multi-core fiberthen all N cores may be utilized in parallel using receiver structure(s)shown previously. Alternatively, if only a single fiber—for example thecenter fiber—emits light and the remaining fibers—or a subset of theremaining fibers—may simultaneously be used to collect light reflectedfrom the sample(s). One particular advantage to this approach that willbe readily appreciated by those skilled in the art is that beam waistsare in the same—but not necessarily exact same) location and additionalinformation about angular scattering and back reflection of light fromthe sample may be obtained and used to differentiate tissue structure.Of further advantage, using one (or more) of the individual fiberscomprising the multi-core optical fiber to illuminate and using otherfibers to collect light reflected from the sample(s) may be extended toany of the embodiments contemplated herein or derivatives thereof.

FIG. 7(C) shows yet another illustrative embodiment of a multi-coreoptical fiber endoscope 702 according to an aspect of the presentdisclosure. In particular, a lens employed may advantageously be a GRINlens or a section of multimode fiber exhibiting a property to imagefacets of the multi-core fiber at an appropriate distal beam focus. Theuse of a multimode fiber, as is known in the art, is particularlyattractive since it may be fusion spliced or otherwise easily secured tothe end of the multicore fiber.

As may be appreciated, it is sometimes advantageous to use a section ofcoreless fiber positioned before the multimode fiber in the optical pathto allow beam(s) to more freely expand. Once the beam diameter is ofsufficient size to achieve the focal depth and confocal parameter thebeam may enter a beam propagation region 735. Once the beam(s) aresufficiently spatially separated an optional distal beam deflector 740element can be used to deflect some of the beams 742 substantially awayfrom the axis of the endoscope and allow one or more or no beam to passthrough substantially uninterrupted to allow for forward ranging 743.The endoscope can have transparent windows at appropriate beam exitlocations and as noted previously—when smooth—allows for easierinsertion into tight spaces. Similarly, an outer sheath of the endoscopebody may be made transparent and constructed from a biocompatiblematerials. Finally, it is noted that while the particular application ofthe principles provided in this disclosure have used endoscopes asexamples, the disclosure is not so limited. In particular, aspects ofthis disclosure will apply equally well to using sensors and imagingwithin catheters, guidewires, needles, laparoscopes and othermedical—and non-medical—devices.

FIG. 7(D) shows yet another illustrative embodiment of a forward imagingmulticore fiber endoscope 703 having a multi-element collimating lensand distal beam deflector element 740. More particularly—and as depictedin that Figure—a multi-element fiber/lens coupling element 720 isemployed to individually collect light from each of the individualmulticore fiber outputs 715 and direct/focus it such that the light maybe more particularly directed onto/into a sample (not specificallyshown). In a particular illustrative embodiment, such multi-elementfiber/lens coupling element 720 may comprise a multi-mode, multicoreoptical fiber that is fusion spliced or otherwise connected to a singlemode multi-core fiber. In an illustrative embodiment, the outsidediameter of the multi-mode multicore fiber is substantially the same asthe outside diameter of the single-mode multicore fiber. Of course,other applications may advantageously utilize configurations in whichthe outer diameters are not the same—for example, those applications inwhich a larger exit beam diameter is desired.

With continued reference to FIG. 7(D), it may be observed that in anillustrative embodiment the multi-mode multi-core fiber is configuredwith an appropriate GRIN-like profile to achieve appropriate beamparameters for example, focal distance, confocal parameter, etc. forimaging light onto/into the sample (not specifically shown).Additionally, it may be observed that the illustrative embodiment shownin the FIG. 7(E) includes a beam deflector element, that is configuredto direct one or more light beams 742 in a direction substantially awayfrom the endoscope axis 751 such that they may be directed to thesample.

FIG. 8 shows yet an additional illustrative example according to thepresent disclosure in which a multicore fiber 810 is coupled to aphotonic integrated circuit (PIC—or Integrated Optical Substrate) 820.As will be readily appreciated by those skilled in the art, there exista wide variety of PIC technologies and materials including PLC, InP andthe entire family of Silicon Photonics materials. As depicted in theFigure, light from the multicore fiber 810 is butt coupled to theintegrated optic substrate through which it propagates via light guides830 formed therein, and subsequently impinges on respective surfacegrating coupler(s) 835. Those skilled in the art will readily understandand appreciate the operation of 1D and 2D surface grating couplers andthat any among a variety of same may advantageously be employed instructures according to the present disclosure. Further appreciated, isthe fact that the surface grating couplers individually collectdiverging light from each of the fibers in the multicore fiber andsimultaneously reemit it in such that it is directed into a sample (notshown). Conversely, such surface grating coupler(s) operate in thereverse direction by collecting light from sample(s) and directing it tothe fibers comprising the multicore fiber.

Turning now to FIG. 9 , there is shown an additional illustrativeexample of multicore optical fiber endoscope distal end 900 according toyet another aspect of the present disclosure. More particularly and asdepicted in that Figure, the multicore optical fiber 930 is showncoupled to a photonic integrated circuit 920. As depicted therein, lightfrom the multicore fiber (not specifically shown)—which is butt coupledto the integrated substrate of the PIC 920 wherein it propagates viawaveguide structures 925 to one or more surface grating coupler(s) 935.As depicted in this illustrative example, inner grating couplers 935couple light to/from the waveguides 930 and multicore optical fiber aswell as additional waveguides 939 which convey light from inner couplers935 to/from outer surface grating couplers 937 which emit/receive lightto/from sample(s).

For simplicity, only a single waveguide is shown connecting opticalfibers to respective inner surface grating couplers and subsequently toouter grating couplers. Notably, two or more waveguides may be employedto couple the optical fibers to the inner grating as well as two or morewaveguides to couple the inner grating couplers to the outer gratingcouplers such that one or two polarization modes are conveyed. Notefurther that the number of waveguides connecting the couplers does nothave to be the same for each. As will be appreciated, configurationsaccording to the present disclosure such as that shown in FIG. 9 providean advantage namely that the radius of the multicore fiber employed maybe smaller and still provide a large aperture on emitting surfacegrating coupler.

FIG. 10 shows yet another illustrative example according to the presentdisclosure of a multicore optical fiber endoscope configuration 1000wherein the multicore optical fiber 1030 is coupled to a photonicintegrated circuit (integrated optical substrate) 1020. Here, theindividual cores 1031 of the multicore fiber 1030 are directly buttcoupled to a surface grating coupler(s) 1035 fabricated in/on thecircuit substrate 1020. The surface grating coupler(s) so coupled to thefibers 1031 are further coupled to respective end facet emitter(s) 1037via respective optical waveguide(s) 1039. As configured, the end facetemitter(s) 1037 emit light substantially orthogonally to the axis of themulticore fiber (except for a center core). As will be understood andappreciated by those skilled in the art, there exist a number of endfacet (horizontal) couplers that may be used including adiabaticcoupling approaches. Advantageously—with a configuration such as thatdepicted—if the wavelength employed is 1300 nm and a focal distance of 2mm is desired, with a beam waist of ˜20 um, then a beam waist at theexit facet is ˜46 um.

At this point it is noted that a number of the illustrative embodimentsshown exhibit a central fiber comprising the multicore fiber which isshown in the Figures to emit light along the axis of the fiber(forward). As will be appreciated, such emission—while desirable incertain applications—is not necessary in all. Additionally, it is notedthat the individual fibers comprising the multicore fiber do not allhave to be the same. In particular, a combination of different fibersmay be employed where—for example—some fibers are single mode whileothers are multimode fibers. Further, some of the fibers may be employedfor imaging and sensing while others may be used for invasive or othertherapeutic procedures or other diagnostic modalities.

As will be appreciated, in many optical systems, including OCT systems,there is a tradeoff made between the measurement range (e.g. theconfocal parameter or 2× the Rayleigh Range) and the resolution at thebeam waist. Generally, the tighter the beam waist, the higher thelateral resolution but the shorter the measurement range. One of theattractive features of PIC and other integrated optical designs is thatby using the high-resolution lithographic techniques for manufacturingthe PICs one can make very complex amplitude and/or phase masks in thesurface gratings.

For example, Bessel beam generation, and other similar depth-of-filedextension techniques, may be designed into the phase mask to provideextended measurement range for a given lateral resolution. Suchdepth-of-field extension techniques, can be designed into the surfacegrating couplers using PIC design tools and are advantageouslyapplicable embodiments according to the present disclosure shown anddescribed.

As noted previously, one of the advantages of using a multicore fiber isthat it allows several simultaneous beams to be guided up/down theendoscope for sensing, imaging, and ranging. One application of such anendoscope acquires several readings of an interior dimensions of a lumenand/or measures properties of interest of the lumen wall. While a singlecore configuration having a distal motor or a rotating fiber (as isknown in SS-OCT cardiovascular and gastroenterology systems) can producea continuous measurement of a lumen, such an approach comes with noteddisadvantages including increased cost, size, and complexity of theendoscopic probe. Multicore fiber configurations according to thepresent disclosure have the potential to be smaller and therefore beemployed into tighter lumens and medical devices (e.g. imaging needles).

Of further advantage, it is possible to include additional measurementor imaging capability to multi-core fiber endoscopes constructedaccording to the present disclosure. Turning now to FIG. 11 there isshown a multicore fiber endoscope 1100 including a pull-back (orpush-back) and/or torsional element 1150 Such an element allows for themanual and/or automated pulling-back (or pushing forward) of the distalend of the endoscope along the axis of the endoscope body and lumen inwhich it is positioned. In this manner, optical measurements may be madealong the axis of the lumen which advantageously allows severaltwo-dimensional images to be obtained. Alternatively, and in anotherillustrative embodiment, the entire multi-core fiber may be rotated backand forth (to and fro) as to radially scan the distal end of theendoscope and therefore the lumen/sample. This advantageously allowsadditional regions of the sample to be measured. It is also contemplatedto have both pullback capability and twisting back and forth capability.

Note further that illustrative embodiments according to the presentdisclosure have depicted a number of ways to image light from amulticore fiber into a sample. There are of course other methods andcombinations of the methods shown that may be implemented and arecontemplated herein. Additionally, there are also many other aspects ofa fiber endoscope design known in the art while not specifically shownand described. Such aspects include protective jackets (metal orplastic), torque cables, markers for x-ray, CT, or MM imaging, etc. Withthis disclosure and teachings in place, those skilled in the art willreadily understand and appreciate that there are numerous applicationsof structures and techniques according to the present disclosure inaddition to SS-OCT and endoscopes including—but not limitedto—catheters, guidewires, imaging needles, laparoscopes, and othermedical and non-medical devices.

At this point those skilled in the art will readily appreciate thatwhile the methods, techniques and structures according to the presentdisclosure have been described with respect to particularimplementations and/or embodiments, those skilled in the art willrecognize that the disclosure is not so limited. Accordingly, the scopeof the disclosure should only be limited by the claims appended hereto.

The invention claimed is:
 1. An optical instrument comprising: a) anoptical source that generates an optical beam at an output; b) amulticore fiber comprising an input optically coupled to the output ofthe optical source and comprising at least two optical fiber cores thatare configured to deliver and collect light from a sample locatedexternal to the multicore fiber; c) fixed distal optics opticallycoupled to a distal end of the multicore fiber, the fixed distal opticsconfigured such that light from one of the at least two optical fibercores is directed in a first fixed direction with respect to an axis ofthe multicore fiber and light from the other of the at least two opticalfiber cores is directed in a second fixed direction with respect to theaxis of the multicore fiber wherein the first fixed direction and thesecond fixed direction are different and d) a receiver having an inputoptically coupled to each of the at least two optical fiber cores, thereceiver configured to receive light collected from the sample andinterferometrically combine the received light collected from the samplewith light collected from a reference path, wherein theinterferometrically combined light from the different optical fibercores having traversed different optical delays along their path fromsource to interferometric combining such that the interferometricallycombined light from the different optical fibers cores show up inparallel at different intermediate frequencies (I.F) when converted intoan electrical signal, so that an intermediate frequency is associatedwith light directed in the first fixed direction with respect to theaxis of the multicore fiber and a different intermediate frequency isassociated with light directed in the second fixed direction withrespect to the axis of the multicore fiber, and so that the electricalsignal can be separated and processed to yield information about thesample from measurements at two different fixed directions with respectto the axis of the multicore fiber.
 2. The optical instrument of claim 1wherein each of the at least two fiber cores operate as a single modefiber at the wavelengths of light of the optical source.
 3. The opticalinstrument of claim 2 wherein the optical source comprises a sweptsource laser.
 4. The optical instrument of claim 2 wherein the receivercomprises a dual-balanced optoelectronic receiver.
 5. The opticalinstrument of claim 2 wherein the receiver comprises a dual-balanced anddual-polarization optoelectronic receiver.
 6. The optical instrument ofclaim 2 wherein the receiver comprises a photonic integrated circuit(PIC).
 7. The optical instrument of claim 1 further comprising apull-back element configured to pull back a distal end of the opticalinstrument.
 8. The optical instrument of claim 1 wherein the first fixeddirection comprises a fixed direction substantially away from the axisof the multicore fiber and the second fixed direction comprises a fixeddirection substantially along the axis of the multicore fiber.
 9. Theoptical instrument of claim 8 wherein the first fixed directioncomprises a direction with an axis having an angle of 45-degrees awayfrom the axis of the multicore fiber.
 10. The optical instrument ofclaim 8 wherein the first fixed direction comprises a direction with anaxis having an angle of 90-degrees away from the axis of the multicorefiber.
 11. The optical instrument of claim 8 wherein the first fixeddirection comprises a direction with an axis having an angle of135-degrees away from the axis of the multicore fiber.
 12. The opticalinstrument of claim 8 wherein the electrical signal being separated andprocessed to yield information about the sample from measurements at twodifferent fixed directions with respect to the axis of the multicorefiber comprises the electrical signal being separated and processed toyield information about the sample from a forward axial measurement anda cross-sectional measurement.